Chronic cervical compressive myelopathy in horses: patterns of astrocytosis in the spinal cord.

The researchers investigated the morphological changes of a type of cell called astrocytes in the spinal cords of healthy horses and those suffering from a condition known as chronic compressive myelopathy, a long-term spinal cord compression.

Methodology

• The researchers used a technique known as immunohistochemical staining, specifically for a protein called glial fibrillary acidic protein, to visualize the astrocytes in the spinal cords of the horses.
• They observed and compared the distribution and physical characteristics of these astrocytes in both healthy horses and those with chronic compressive myelopathy.

Findings in Normal Horses

• In healthy horses, the astrocytes displayed irregular distribution in the gray matter of the spinal cord.
• The cell bodies of these astrocytes exhibited different shapes and sizes depending on their location in the spinal cord. Near the gray matter, they were smaller and angular, while they were larger and star-shaped in the subpial area (the outermost layer of the spinal cord).
• The astrocytes processes, or extensions, were fine and displayed a predominantly radial pattern.

Findings in Horses with Chronic Compressive Myelopathy

• In horses with the chronic myelopathy condition, the researchers noted significant gliosis, which refers to a reactive response by the astrocytes in response to damage in the central nervous system.
• In the gray matter, astrocytes often appeared enlarged and rounded, but the gliosis was generally mild.
• In the white matter of the spinal cord where there was swelling and nerve fiber degeneration due to the compression, the gliosis was more evident. The fine radial arrangement of astrocyte fibers was replaced by a denser, more irregular pattern.
• Gliosis was observed to persist even after nerve fiber degeneration had ceased.
• The regions of gliosis corresponded with areas that showed staining for myelin degeneration and myelin loss, suggesting that the astrocytes were replacing the areas left void after the degeneration of the nerve fibers.

Conclusion

• The researchers concluded that astrocytic gliosis is a significant and persistent change in the spinal cords of horses affected by chronic cervical compressive myelopathy. This finding could provide valuable insights into the progression and potential treatment strategies for this debilitating condition in horses.